The present invention relates to a device for manufacturing a groove bearing having a bearing shaft and a bearing bush with cooperating bearing surfaces, of which at least one bearing surface is formed with a pattern of pumping grooves.
A device for forming such grooves has been taught in EPA2292. This device, shown in FIG. 1 hereof, comprises a hard pin around which a cylindrical cage is arranged which has one or more annular patterns of holes arranged symmetrically about the central axis of the cage. These holes are engaged by hard balls having a diameter larger than the wall thickness of the cage. The cage and the pin or sleeve are each coupled to a drive arrangement capable of impressing a translation and a rotation upon the cage and the pin or sleeve. Thus, the cage and pin or sleeve are separately translated and/or rotated in order to form the grooves in the surface of the bearing wall. According to the patent owner's own later filed U.S. Pat. No. 5,265,334, it has been found that in carrying out the prior art method the pin or sleeve of the prior art device is subjected to substantial wear as a result of large Hertzian stresses produced at the contact surfaces between the pin or sleeve and the balls. The wear particularly causes deformations of the pin or sleeve surfaces surrounding and facing the cage, so that the contact surface of the pin or sleeve becomes irregular resulting in inaccurate groove depth. Therefore, this same U.S. Pat. No. 5,265,334 disclosed an improvement thereof shown in FIG. 2 of the present application in which the bearing surface of the bearing part (which may be a pin or sleeve) includes a continuous groove which is concentric with the central axis of the pin or sleeve, the groove extending in a longitudinal sectional plane of the pin or sleeve which contains the central axis. However, this also results in continuous wear of a single portion of the surface of the pin resulting in an unnecessarily short life for the device for making grooves.